President Obama warned in 2011 that the possibility of a “lone wolf” terrorist attack — similar to what the Boston bombings appear to be — was the greatest national security threat America faced in the post-9/11 age.

Obama was speaking with CNN’s Wolf Blitzer weeks before the 10th anniversary of the Sept. 11 attacks that killed more than 2,000 people.

“The biggest concern we have right now is not the launching of a major terrorist operation, although that risk is always there. The risk that we’re especially concerned over right now is the lone wolf terrorist,” the president said. “Somebody with a single weapon being able to carry out wide-scale massacres of the sort that we saw in Norway recently. You know, when you’ve got one person who is deranged or driven by a hateful ideology, they can do a lot of damage, and it’s a lot harder to trace those lone wolf operators.”

The president continued, adding that intelligence agencies were staying “vigilant” against terrorist threats, especially in the wake of the anniversary of the Sept. 11 attacks.

“We’re spending a lot of time monitoring and gathering information,” he said. “I think that we generally have to stay vigilant. There may be a little extra vigilance during 9/11.”

He continued, “I think the most likely scenario that we have to guard against right now ends up being more of a lone wolf operation than a large, well-coordinated terrorist attack. We still have to stay on top of it, though, and we’re never letting our guard down, that’s part of our job.”

According to reports Tuesday, Boston bombing suspect Dzhokhar Tsarnaev told FBI investigators that he and his brother operated alone and without aid from terrorist organizations. The Los Angeles Timesreported terrorist experts, such as Brian Jenkins of RAND Corporation, suspect the brothers follow a pattern of alienated youth self-radicalizing.

New York Congressman Peter King, the former chairman of the House of Representatives Homeland Security Committee, said Wednesday it was too early to say if the Tsarnaev brothers attacked alone.

“I don’t see how we can accept that,” King said, according to The Hill. “It may end up being the truth, but this is a person who is a mass murderer. He’s a person who barely can speak, speak at all. I don’t see why he would be giving up any accomplices anyhow or talk about any connections his brother might have had in Chechnya or Russia.”